Bond angle: 109.5 degrees

Explanation:

- Sodium sulfate is a compound with the chemical formula Na2SO4. It consists of two sodium ions (Na+) and one sulfate ion (SO4^2-).

- The sulfate ion is a polyatomic ion with a central sulfur atom surrounded by four oxygen atoms. The sulfur atom has a +6 oxidation state, and each oxygen atom has a -2 oxidation state.

- The tetrahedral shape of the sulfate ion is due to the fact that the sulfur atom has four valence electrons, which are used to form four single bonds with the oxygen atoms.

- The bond angle between the sulfur atom and each oxygen atom is 109.5 degrees. This is the ideal bond angle for a tetrahedral molecule, and it is due to the fact that the four oxygen atoms are arranged in a tetrahedral shape around the sulfur atom.